Musnad Ahmad #91

It was narrated that 'Abdullah bin 'Abbas said: I heard 'Umar bin al-Khattab say: When ‘Abdullah bin Ubayy died, the Messenger of Allah ﷺ was called to offer the funeral prayer for him, and when he stood by the deceased and was about to offer the prayer for him. I went and stood before him and said: O Messenger of Allah, (will you offer the funeral prayer) for the enemy of Allah who said such and such? and I listed what he had done. And the Messenger of Allah ﷺ was smiling until when I had said too much, he said: `Move away from me, O ‘Umar, for I was given the choice and I have chosen. It was said: `Whether you (O Muhammad) ask forgiveness for them (hypocrites) or ask not forgiveness for them- (and even) if you ask seventy times for their forgiveness-Allah will not forgive them' . So after that the Messenger of Allah ﷺ did not offer the funeral prayer for any hypocrite or stand by his grave until he passed away.